The invention is directed generally to transformers for environmental lighting systems, and more particularly to a transformer assembly for minimizing voltage drop in a low voltage environmental lighting system.
Environmental lighting systems typically operate by providing low voltage to a number of lamps which are located to enhance various features in the environment, such as statues, trees, or flower beds, or to illuminate traffic areas for safety. The low voltage, usually 12 volts, is produced by one or more transformers that are connected to a 120 VAC source and positioned within the area covered by the lighting system in a way to ensure a stable voltage supply to the lamps. When using only one transformer, it is important to center the transformer on the wattage load. A primary goal in laying out low voltage lighting systems is to minimize cable runs because of the adverse affect voltage drop has on lamp performance and lifetime. Furthermore, the copper direct burial cable used in low voltage lighting systems is expensive, so the lengths of cable runs are preferably minimized for economy as well. Cables to lamps at the greatest distance from the transformer require an initially higher output voltage and/or a heavier gauge cable in order to compensate for the voltage drop over long stretches of cable and multiple lamps. The use of multiple transformers within a system provides better lamp performance as long as each transformer is placed to minimize cable runs. Also, multiple transformers permit selective control of light in different zones within the overall lighting system.
Most existing transformer assemblies were built for industrial applications, i.e., they are not designed with aesthetics in mind. Furthermore, the transformers are traditionally hung on a post or wall in a rain-tight box, so that they are at least one foot (0.3 m) above the ground (to comply with NEC (National Electrical Code) requirements.) Thus, in order to avoid detracting from the overall appearance of the lighted area, it is generally preferred that the transformer be placed inconspicuously, on the side of a building or inside a structure. This is a problem, however, in areas such as island planters surrounded by traffic or seating areas, or by a decorative feature such as a pond or pool, which rarely provide any suitable cover for concealing the unattractive box. There are also vandalism and safety concerns which influence the decision in placement of the transformer box in a hidden location. The desire to conceal the box, however, increases the challenge in minimizing the distance between the lamps and the transformer.
One solution to the difficulty in placement of conventional transformer boxes is to use direct burial transformers, which can be located close to the lamps without being an eyesore. However, such transformers suffer from a range of problems since it is almost impossible to completely waterproof a buried enclosure since the installer must run both 120 V input and 12 V output wiring into and out of the enclosure. Also, the user needs relatively easy access to the interior to reset circuit breakers, which have a greater tendency to fail in humid conditions, such that factory seals at both the top and bottom of the enclosure are broken. These problems are combined with the siphoning phenomenon caused by the heating and cooling of the interior of the enclosure, virtually guarantying that the transformer will fail over time.
Accordingly, the need remains for a transformer assembly for low voltage lighting systems which can be safely placed so as to minimize the lengths of cable needed to reach the lamps without detracting from the appearance of the area to be lighted. The transformer assembly described herein is addressed to and provides a solution for such a need.
In an exemplary embodiment, the transformer assembly comprises a housing with a top portion having a cavity within which a transformer is sealed using a waterproof sealant and a body portion which is generally hollow for supporting the top portion and for providing a pathway for feeding wires into the housing for connection to the transformer. The transformer is mounted on a plate retained within the cavity in the top portion of the housing. The plate, which has a plurality of holes therethrough, supports at least one circuit breaker and at least one liquid-tight fitting through which wires are passed to connect to the transformer. The at least one circuit breaker is positioned over an opening through the plate allowing access to its reset switch. The at least one circuit breaker is sealed within flexible silicone boots so that both the top and bottom of the circuit breaker are sealed against moisture while still allowing the reset switch to be pressed. The top portion, which in the preferred embodiment is generally dome-shaped, is filled with epoxy within encases the transformer, the at least one circuit breaker and upper boot, the upper surface of the plate, all fasteners that are used to attach the transformer and at least one circuit breaker to the plate, and the upper ends of the liquid tight fittings.
In the preferred embodiment, the top portion of the housing is formed from copper which will patine into natural shades of greens and browns to complement a garden setting. Alternatively, the top portion can be a powder-coated metal in a color that will fit into the surrounding area. A lip formed on the lower edge of the top portion has a diameter adapted to fit over the outer diameter of the body portion. Slots formed in the lip allow a screw or other fastener to pass through into a threaded opening in the body portion to fasten the top portion to the body. The body portion can be formed from plastic, polymer, powder-coated metal, copper, brass or other material. A plurality of vertically-extending channels or ribs are formed in the outer surface of the body portion to prevent the top portion from seizing up and preventing removal of the top from the body portion. In the preferred embodiment, the body portion is a hollow cylinder, i.e., has a circular cross-section, however, other shapes may be used, including those having a cross-section that is an oval, or a polygon such as a triangle, square, hexagon, octagon, etc.